at least 3 rails

In some parts of the UK, they do use 4 rails.  One is DC +, the other DC -.  The other two rails are for the regular railroad wheels.  I have heard the 4 rail system prevents electrical leakage compared with the return electricity using the running rails.

That's going to be a tough one to figure out.  

• It isn't a gantlet track, as the gauge of the two tracks is not the same.
• It isn't new rail laid down to replace the existing rail, because -- in the era of the photo -- the rails would be 39 feet long instead of appearing to be continuous.

(Sound of me rubbing my chin and scratching my head)

Possibly in the Australian state of Victoria, which had standard gauge AND broad gauge trains, along with some North American-appearing equipment?

I believe that system is seen on the subway and surface lines in London, England. You can see the running rails vs. the power rails in this pic: 

http://i.telegraph.co.uk/multi...e_train_1113751c.jpg

And an explanation:

http://www.trainweb.org/tubeprune/tractioncurr.htm

Firewood posted:

I believe that system is seen on the subway and surface lines in London, England. You can see the running rails vs. the power rails in this pic: ...

spot-on for all four rails, ...thanks!

interesting that the documentary was referring to a train to upstate NY in the 1930's when the clip was shown.  well that mystery is solved.  must be fun to watch in the rain!

cheers...gary

Look at the coach.  Very British in looks!

See, see, 3 rail O Scale is prototypical !

Might the original photo, which appears to have old, wooden equipment, be depicting 3 gauges of track - 2', 3' and standard gauge?    Perhaps Africa or, as noted, perhaps Australia?

The London Underground (subway system) has an extensive 4-rail system, to avoid using the running rails as a ground return for traction current because it caused electrolysis damage to other underground metal items such as water mains and tunnel components. That first picture is undoubtedly from the London area, decades ago. Many parts of the system run above ground, not all tunnels.

It's been a while since I've seen them up close, but sections of concrete-tied rails have a remarkable resemblance to the sloped look of Lionel Super 0.

NYC subway and Houston METRO Light Rail have had past issues with stray current.  Both use the running rails for return current.

Another place you see 4-rail set-ups is in Chicagoland. Some commuter stations have sort of a gauntlet track set up, where passenger trains use the rails bringing the train close to the platform. Freight trains using the same line need more clearance, so use the tracks farther from the platform.

I think the B&P Tunnels in Baltimore had a like trackage so tri-racks could clear it.